JP3486278B2 - Pneumatic tire - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having an improved rubber composition for a tread portion.

[0002]

2. Description of the Related Art In recent years, tire tread rubbers, particularly high performance tire tread rubbers, have been subjected to wear resistance, fracture characteristics,
There is a strong demand for an overall balance of wet grip characteristics (wet skid resistance) and dry grip characteristics on a lubricated road surface at a high level.

In response to such requirements, these performances are associated with the rubber composition, and in order to improve the grip characteristics, the hysteresis loss of the tread rubber is increased, that is, Tan δ is viscoelastically. It turns out that it needs to be bigger. In order to improve wear resistance and high-speed durability, tensile strength, especially high temperature (100
It has also been found that it is necessary to increase fracture properties such as tensile strength at (° C) and elongation at break.

Conventionally, various rubber compositions have been developed for the purpose of satisfying the above-mentioned various properties. Specifically, (1) a technique for blending rubber is to use styrene / butadiene copolymer and butyl rubber (Japanese Patent Publication No.
No. 51501), polynorbornene (Japanese Patent Application Laid-Open No. 6-68242).
2-143945 and JP-A-2-142838), or polyisoprene rubber (JP-A-63-1).
(See Japanese Patent No. 32949)) and the like,
In addition, as a technique (2) using an additive, a softening agent, etc., there is a technique using a coumarone indene resin (see JP-A-62-1735), and (3) a novel styrene-butadiene copolymer. As a technique of using a polymer, a styrene-butadiene copolymer whose terminal is modified with a diphenylmethanol-based compound (see JP-A-60-61314)
Alternatively, a diblock styrene / butadiene copolymer composed of two blocks having different composition ratios of styrene and butadiene (see JP-A-1-131258) is used.

However, the above-mentioned rubber composition cannot sufficiently satisfy the actually required high levels of wear resistance, fracture characteristics, grip characteristics and fuel consumption characteristics, and the balance at these high levels. There wasn't.

Further, by adding a large amount of a softening agent or the like, the grip characteristics can be increased, but in this case, the breaking characteristics and the wear resistance tend to be impaired.

As described above, in order to improve grip characteristics, it is necessary to increase the hysteresis loss of the rubber composition, but in this case, the rolling resistance also increases, which is desirable for the fuel consumption characteristics of tires. Absent. In the prior art, it was almost impossible to improve these two properties at the same time.

[0008]

In order to solve the above-mentioned inconveniences, the present invention improves the rubber composition used for the tread portion, so as not to impair the fracture characteristics and the wear resistance, and to have a low hysteresis loss characteristic. It is an object of the present invention to provide a high-performance pneumatic tire that has both (fuel consumption characteristics) and high grip characteristics.

[0009]

In order to achieve the above object, a pneumatic tire according to the present invention has the following constitution. (1) 50% styrene-butadiene copolymer (SBR)
With respect to 100 parts by weight of the rubber component containing more than 1% by weight
A rubber composition containing 2 to 50 parts by weight of a rubber-reinforced thermoplastic resin composed of 10% by weight or more of a conjugated diene rubber component and the remainder being a resin component having a glass transition temperature (Tg) of 100 to 160 ° C. is used in a tread portion. It is characterized by having done. (2) The styrene-butadiene copolymer (SBR)
Contains 20 to 50% by weight of styrene. (3) The conjugated diene rubber component is 35 to 65% by weight. (4) The conjugated diene rubber component used for forming the rubber-reinforced thermoplastic resin is polybutadiene or styrene-butadiene copolymer (SBR) having a toluene insoluble content of 5% or less. (5) The resin component of the rubber-reinforced thermoplastic resin is a polymer containing at least one vinyl monomer selected from the group consisting of acrylonitrile, styrene, α-methylstyrene, and divinylbenzene. Is characterized by.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

The rubber component as the matrix rubber of the rubber composition according to the present invention contains 50% by weight or more of the styrene / butadiene copolymer, but the balance rubber component is
Diene rubbers such as natural rubber, polyisoprene rubber, and polybutadiene rubber can be preferably used alone or as a mixture thereof.

The rubber composition according to the present invention includes a filler such as carbon black and silica, a softening agent such as aroma oil and spindle oil, an antiaging agent, a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerator. Needless to say, a proper amount of a compounding agent that is usually compounded, such as an auxiliary agent, can be appropriately compounded.

The operation of the present invention will be described below. The rubber-reinforced thermoplastic resin compounded in the rubber composition according to the present invention, under normal tire use conditions, functions similarly to a filler such as carbon black, and the compatibility of the resin / matrix rubber interface, Since it has excellent co-vulcanization properties, it functions as an elastic body and has a property of low hysteresis loss.However, in the high strain / high input region where gripping force is required, the resin phase undergoes plastic deformation, resulting in high The characteristics of hysteresis loss can be brought out. By using a rubber composition in which the resin phase controls the conditions for changing from elastic deformation to plastic deformation in a tire tread, fracture characteristics,
It is possible to obtain a pneumatic tire that has both low hysteresis loss characteristics (fuel consumption characteristics) and high grip characteristics without impairing wear resistance.

When the content of the conjugated diene rubber component is less than 10% by weight, the covulcanizability with the matrix rubber is remarkably deteriorated, and the rubber-reinforced thermoplastic resin acts as a mere foreign substance, resulting in a large decrease in fracture characteristics. Also, for the same reason,
It does not contribute to the improvement of grip characteristics. Desirably, the conjugated diene rubber component is in the range of 35 to 65% by weight. This is because when the conjugated diene rubber component exceeds 65% by weight, the characteristics as a resin deteriorate and the grip characteristics are not significantly improved.

The glass transition temperature (Tg) of the resin component obtained by polymerizing the vinyl monomer needs to be in the range of 100 to 160 ° C. This is because when the temperature is lower than 100 ° C., the resin component tends to be softened in the normal use temperature range of the tire, which causes deterioration of rolling resistance and wear resistance. Further, when it exceeds 160 ° C., it is difficult to obtain a good dispersion of the rubber-reinforced thermoplastic resin in the matrix rubber by the usual rubber kneading method, which leads to deterioration of the fracture property,
Also, the resin cannot easily cause plastic deformation, and the improvement of grip characteristics is not sufficient. Moreover, the compounding amount of this rubber-reinforced thermoplastic resin is defined as 2 to 50 parts by weight with respect to 100 parts by weight of the rubber component. When the amount is less than 2 parts by weight, the effect of the resin is extremely small and If it exceeds, the function as a rubber composition is weakened, and the rubber composition functions as a resin, resulting in a significant decrease in wear resistance.

When the toluene-insoluble content of the conjugated diene rubber component is higher than 5% in the crosslinked state, the interface with the rubber matrix is not sufficiently reinforced, which tends to lower the overall fracture characteristics.

When the content of styrene-butadiene copolymer (SBR) in the rubber component is less than 50% by weight, the rubber composition does not have sufficient grip properties, and the styrene portion of SBR is less than 20% by weight. Even if it does not exist, the grip property is not sufficient, and when it exceeds 50% by weight, the fracture property is remarkably deteriorated, and the hardness of the rubber composition tends to be too high.

[0018]

EXAMPLES The present invention will be described below based on Examples, Reference Examples and Comparative Examples.

The rubber-reinforced thermoplastic resins (A to
J) and SBR (a to o) described in Table 2 were used to prepare rubber compositions with the compounding formulations shown in Tables 3 and 4. In Table 4, the amount of resin and the amount of aromatic oil blended are shown in parts by weight when the rubber components (SBR and BR) are 100 parts by weight.

Using these rubber compositions in the tread portion of tires, various test tires of 165SR13 were prepared in accordance with a conventional method, and various measurements were carried out according to the following methods.
Regarding the breaking characteristics and abrasion resistance, the rubber compositions shown in Tables 3 and 4 were vulcanized at 145 ° C. for 30 minutes.

Content of conjugated diene rubber component in Table 1,
The methods for measuring the toluene insoluble content and the glass transition temperature (Tg) are as follows.

(1) Measurement of content of conjugated diene rubber component (a) Resins A, B and J Sample rubber reinforced thermoplastic resins were decomposed by the following thermal decomposition equipment and then by gas chromatography (GC). Separate each ion and use a flame ionization detector (Flame lonization D
Etector: FDI) was used to quantify the amount of butadiene with a calibration curve prepared in advance using butadiene rubber (therefore,
When the rubber is SBR, it is necessary to know the amount of styrene in the rubber component in advance. ) Thermal decomposition apparatus JHP-3 type decomposition condition manufactured by Japan Analytical Industry Co., Ltd. 590 ° C., 3 seconds GC HP5890A column DB1 (length 30 m manufactured by J & W Scientific) measurement temperature range 70 ° C. to 300 ° C. temperature increase rate 15 ° C./min (a) ) Resins C to I Calculated from the charging ratio of the monomer of the resin component and the rubber component, and the degree of polymerization.

(2) Measurement of Toluene Insoluble Content 1 g of the conjugated diene rubber component is added to 100 ml of toluene, and the mixture is left standing at room temperature for 48 hours. The insoluble matter was separated by filtration through a 100-mesh wire net, the filtrate was taken, toluene was removed and dried to obtain a toluene soluble matter (Xg), and the toluene insoluble matter was calculated from the following formula. Toluene insoluble matter (%) = {(1-X) (g) / 1
(G)} × 100

(3) Measurement of glass transition temperature (Tg) The glass transition temperature (Tg) was measured by using a differential thermal analyzer (DSC200) manufactured by Seiko Instruments Inc.
0 ml / min. At 10 ° C./min. At a heating rate of -1
It measured about 20-180 degreeC.

[0025]

[Table 1] A: Product name ABS10 (manufactured by Japan Synthetic Rubber Co., Ltd.) B: Product name Califlex 1101 (manufactured by Shell Chemical Co., Ltd.,
SBR Copolymer) CG, I: Synthetic product The synthetic method is as follows. In a reaction vessel equipped with a reflux condenser, a thermometer and a stirrer, a conjugated diene rubber component shown in Table 1 synthesized in advance by emulsion polymerization, 3 parts of disproportionated rosin acid soap, 0.2 part of t-dodecyl mercaptan, and The vinyl-based monomer components shown in Table 1 were charged, and 0.25 part of sodium pyrophosphate, 0.35 part of glucose, 0.005 part of ferrous sulfate, and 0.6 part of cumene hydroperoxide were added to carry out polymerization. The reaction was started for 4 hours.
Sulfuric acid was added to the obtained copolymer latex to coagulate, washed with water and dried to obtain a rubber-reinforced thermoplastic resin (C to G, I). H: Synthetic product, styrene-poly-α-methylstyrene copolymer (resin C to C except that rubber component is 0 and styrene and α-methylstyrene are used as vinyl monomers)
It was synthesized in the same manner as G and I. ) J: Product name AS230 (acrylonitrile / styrene resin, manufactured by Nippon Synthetic Rubber Co., Ltd.)

The fracture characteristics, wear resistance, rolling resistance and grip performance in Table 4 are measured as follows.

(4) Destruction characteristics The breaking characteristics were measured according to JIS K-6301.

(5) Abrasion resistance With respect to abrasion resistance, a Lambourn type abrasion tester was used to measure the amount of abrasion at a slip ratio of 25% at room temperature, and the reciprocal value was used to obtain the value in Comparative Example 4 as 100. Was displayed as an index. Therefore, the larger the value, the better the wear resistance. (6) Rolling resistance index The tire is brought into contact with a drum having an outer diameter of 1.7 m, the drum is rotated, the drum is allowed to coast to a constant speed, and then the drum is coasted. evaluated. In the table, the value of Comparative Example 4 was set to 100 and displayed as an index. Therefore, the larger the value, the smaller the rolling resistance and the better the rolling resistance.

[0029]

[Equation 1]

(7) Dry Grip Performance Dry grip was evaluated using the tire of 165SR13. It measures the lap time on a clear circuit, which consists of straight roads, curves, banks, etc.,
Using the reciprocal value, the time in Comparative Example 4 is set to 10
The index was set to 0. Therefore, the larger the number,
It shows that the lap time is short and the dry grip performance is excellent.

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

As shown in Table 4, it can be seen that the rolling resistance and the dry grip performance of the respective examples were improved without impairing the fracture characteristics and the wear resistance.

[0035]

As described above, according to the present invention,
It is possible to provide a high-performance pneumatic tire with improved rolling resistance and dry grip performance without impairing the fracture characteristics and wear resistance.

Claims (5)

(57) [Claims] 1. A styrene-butadiene copolymer (SB
R) to 100 parts by weight of the rubber component containing 50% by weight or more of R), and 10% by weight or more of the conjugated diene rubber component and the balance being a resin component having a glass transition temperature (Tg) of 100 to 160 ° C. A pneumatic tire using a rubber composition containing 2 to 50 parts by weight of a thermoplastic resin in a tread portion. 2. The styrene-butadiene copolymer (S
The pneumatic tire according to claim 1, wherein BR) contains 20 to 50% by weight of styrene. 3. The conjugated diene rubber component is 35 to 65.
The pneumatic tire according to claim 1 or 2, characterized in that the content is% by weight. 4. The conjugated diene rubber component used for forming the rubber-reinforced thermoplastic resin is polybutadiene or styrene-butadiene copolymer (SBR) having a toluene insoluble content of 5% or less. The pneumatic tire according to claim 1, 2 or 3. 5. The polymer of which the resin component of the rubber-reinforced thermoplastic resin is a polymer containing at least one vinyl monomer selected from the group consisting of acrylonitrile, styrene, α-methylstyrene and divinylbenzene. It exists, The pneumatic tire of any one of Claims 1-4 characterized by the above-mentioned.